1. Field of the Invention
The present invention relates to an improved method for the manufacture of air bearing sliders for use in a magnetic storage disk drive. More particularly, the invention relates to a method for producing a high camber and crown in air bearing sliders.
2. Description of the Background Art
Magnetic storage disk drives typically include a magnetic transducer called a "head" suspended in close proximity to the magnetic disk, which serves as the recording medium. In Winchester-type disk drives, a magnetic thin film head is embedded in a ceramic block, called a slider, which is then attached to a flexible suspension. During operation, the rotation of the magnetic disk relative to the slider provides an air flow along the surface of the slider, which causes it to lift, so that the slider is supported on a cushion of air. This surface of the slider is referred to as the Air Bearing Surface (ABS). The slider can also be thought of as having a "leading end", into which airflow enters and a "trailing end" from which it exits. The transducer head typically is positioned at the trailing end of the slider, which is generally closer to the disk surface than the leading end. The distance between the head and the disk surface is referred to as the "fly height". It is desirable for the head to fly very close to the disk surface in order to detect and read the information magnetically encoded on the disk surface. For this reason, fly height stability is of crucial importance in the disk drive operation.
The physical shape of the slider's ABS has been found to be important to the fly height. Curvature of the slider along the length from leading end to trailing end has been termed "crown" and is considered to be positive when the curvature is convex, and negative when it is concave. Everything else being equal, positive crown tends to cause the head to fly higher, relative to the disk surface, thus decreasing the head's sensitivity, while negative crown causes the head to fly lower, thus risking contact with the disk. FIG. 1 (Prior Art) illustrates a slider 12 having a leading end 2, a trailing end 4, an upper surface 6, which will be the Air Bearing Surface (ABS) and a lower or back surface 8, and including a transducer 16 in the trailing end 4. The slider 12 in FIG. 1 illustrates positive crown. A dashed horizontal line is provided as reference to demonstrate the arc of the positive crown.
Another factor to be considered in disk drive head design is take-off speed, which is defined as the velocity necessary for a slider to fly at a height above all the surface roughness of the disk. This factor too is influenced by crown of the slider.
When the slider is curved across the width of the unit, this curvature is termed "camber" and can also be positive (convex) or negative (concave). Camber has been found to influence flying and tribological considerations. FIG. 2 (Prior Art) shows a slider 12 having positive camber containing a transducer 16. Again a horizontal reference line is provided to emphasize the degree of curvature of the positive camber.
Presently, it is thought desirable to have both positive crown and positive camber in order to achieve desired fly height, fly height stability, take-off speed and certain other aerodynamic characteristics.
As shown in FIGS. 4 and 5(Prior Art), sliders 12 are typically manufactured by embedding a matrix 14 of transducer elements 16 into a wafer 18, which is then sliced into rows 20. These rows 20 are eventually sliced into individual units 22, producing the individual sliders 12. The top surface 24 of the row 20 is lapped to become the Air Bearing Surfaces (ABS) 26 of the individual slider units.
A historical manner of producing positive crown and camber was by removing small amounts of material from the ABS using a lapping plate having the desired curvature. This was done to individual sliders at the end of the slider fabrication process, and was separate from the row level lapping process in which the sensor height was defined. The processing of individual sliders is not efficient due to their small size.
In current practice, the rows are lapped to the appropriate dimensions, before they are sliced into individual units. In the fabrication process, some rows bow under stress exhibiting what is known as "row bow", (see FIG. 3 (Prior Art), which can produce an unintended result of both positive camber and crown in the sliders, once they are cut apart into individual units. However, there is usually considerable variation in rows with row bow, and it is thus not considered as a controllable method of producing camber and crown in sliders. Row bow is generally avoided in manufacturing, and several schemes have been proposed to eliminate it. Additionally, there are residual stresses left in the straight rows which are produced from bowed rows, and post-lapping stress management of some sort is often required. Efforts directed at relaxing stress can affect reliability. In processing steps which use a laser beam to remove material and straighten bowed rows, there is a risk of thermal damage to the transducers. Also, as new ABS lapping processes are developed, less surface stress is available for stress management, resulting in an upper limit to the positive crown and camber which can be achieved.
Numerous U.S. Patents have addressed the processing of sliders. U.S. Pat. No. 5,266,769 to Deshpande et al discloses producing a stress pattern on the back side of sliders to achieve desired crown and camber. U.S. Pat. No. 5,442,850 to Kerth discloses impinging a section of the slider with a stream of particles to alter the crown and camber. U.S. Pat. No. 5,713,123 to Toyoda et al teaches creating positive crown by alternately lapping the ABS and back side of the slider to cause deformation which produce crown. U.S. Pat. No. 5,771,570 to Chhabra et al discloses a method for shifting the peak point of the crown of a slider by affixing a suspension to the bonding surface of the slider, which causes a displacement force that shifts the peak.
In all of these patents, it appears that the sliders will be arranged in linear rows, and that they will be lapped with flat plates, thus encountering the problems and drawbacks discussed above.
It is, therefore, an object of the present invention to provide an improved method for the manufacture of disk drive sliders which allow the formation of high degrees of crown and camber. A further object is to provide a method which is made more efficient by acting upon entire rows containing multiple sliders, but without the inconsistencies, limitations and post-lapping stress management required by bowed row processing. Other objects and advantages will become apparent from the following disclosure.